<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>

    .box1{
      width:200px;
      height: 200px;
      /* margin-left: -40px; */
      background-color: #bfa;
      /* margin-bottom: 50px; */
      /* margin-bottom: 50px; */
    }
    .box1::before {
        content: "";
        display: table;
    }
    .box2{
      width:100px;
      height: 100px;
      background-color: #aaa;
      margin-top: 100px;
      /* margin-top: -100px;
      margin-top: 10px; */
    }
  </style>
</head>
<body>
  <div class="box1">
    <div class="box2"></div>
  </div>
  
</body>
</html>